Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$183.96	6.592%	$196.0866	$196.09	$196.10	$196.10
Purchase #2	$246.53	3.867%	$256.0633	$256.06	$256.05	$256.10
Purchase #3	$52.69	4.468%	$55.0442	$55.04	$55.05	$55.00
Purchase #4	$144.85	13.423%	$164.2932	$164.29	$164.30	$164.30
Purchase #5	$88.65	7.318%	$95.1374	$95.14	$95.15	$95.10
Purchase #6	$23.98	13.565%	$27.2329	$27.23	$27.25	$27.20
Purchase #7	$83.76	10.253%	$92.3479	$92.35	$92.35	$92.30
7 purchase totals =	$824.42		$886.2055	$886.20	$886.25	$886.10